نشریه نامه انجمن حشره شناسی ایران
سال سی و نهم شماره 3 (پیاپی 79، پاییز 1398)

The volatiles emitted by herbivorous insects and herbivore-damaged plants play an important role in foraging behaviour of parasitoids that lead to host location of parasitic wasps. The olfactory response of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) to volatile compounds of larvae and larval faeces of Helicoverpa armigera (Hünber) (Lepidoptera: Noctuidae), corn ear and tomato fruits both infested and un-infested by cotton bollworm was studied using a double sided Y-shaped olfactometer in laboratory conditions. Results showed that parasitoid wasps were significantly more attracted to compounds emitted by larvae and larval faeces of the cotton bollworm. Response of parasitoid wasps to volatiles of larvae in comparison with infested tomato and corn ear indicated that 71.74% and 68.09% of wasps were attracted to odors of host larvae, respectively. Wasps did not show response to the odors released from un-infested tomato fruit and corn ear. There was no significant difference in attraction of parasitoid wasps to faeces of larvae that fed on tomato and corn ear. Our results indicated that volatile compounds produced by fifth instar larvae and larval faeces of H. armigera are important agents for attracting parasitoid wasps.

The cotton mealybug, Phenacoccus solenopsis Tinsley, is a phytophagous insect with high populations causing serious damage to the Chinese hibiscus shrubs (Hibiscus rosa-sinensis L.) from south of Iran. This research was conducted to determine the host preference of Aenasius bambawalei Hayat when had choice or no-choice access to different stages of cotton mealybug. Moreover, biological characteristics and body size of wasps when reared on third nymphal instar and adult females was studied under laboratory condition. According to the results, female wasps did not parasitize the first nymphal stage. The second nymphal stage was parasitized without any adult wasp emergence. The results revealed that the percentage of mealybug mummified, and sex ratio (% female) was significantly higher when mealybug hosts were parasitized at adult females compared to third nymphal stage, in both choice and no-choice access. The developmental times (days) and body size (hind tibia length and antenna length) of A. bambawalei females and males developing in cotton mealybug adult female was significantly longer than those reared on third nymphal instar. The results indicated the high control ability of A. bambawalei, on the older growth stages of cotton mealybug. It is hoped that this parasitoid wasp can be used as a biological agent to control Ph. solenopsis, on the Chinese hibiscus shrubs, H. rosa-sinensis.

Trichogramma evanescens Westwood is one of the most important biological control agents of lepidopteran pests. This parasitoid is widely distributed throughout Iran. Present study was conducted to assay influence of the age of Ephestia kuehniella Zeller egg on the number of parasitized eggs, developmental time, sex ratio, progeny longevity and fecundity of T. evanescens. Individual mated female parasitoids (E. kuehniella in no-choice experiments. Mean number of parasitized eggs were 32.40 ± 0.04, 29.80 ± 0.05, 26.93 ± 0.16, 23.83 ± 0.06 and 18.91 ± 0.04, respectively. The obtained results showed that different egg ages had a significant effect on the developmental time, sex ratio, progeny longevity and fecundity of the parasitoid wasp. Data analysis demonstrated significant decreasing of net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) with increasing the age of eggs. The highest values for r and λ were 0.390 ± 0.006 day-1 and 1.47 ± 0.008 days, respectively in the eggs with 12h egg. The results of the current study indicated that the egg age is one of the most important factors on life table parameters of T. evanescens and the eggs of E. kuehniella with 12h age are the most suitable eggs for development, reproduction and mass rearing of T. evanescens.

Life history attributes of Habrobracon hebetor Say were investigated at six thermal regimes (20, 22.5, 25, 27.5, 30 and 32.5 ºC, 65±5 % RH and a photoperiod of 16:8 h L:D) using Galleria mellonella L. larvae as lab host. About 80-250 fresh eggs of the parasitoid (Cohort) were reared under different thermal treatments. Incubation period of male and female eggs reduced significantly from 4.12 and 3.45 days at 20 ºC to 1.25 and 1.06 days at 27.5 ºC, respectively. Larval development was 7.00 and 6.81days for male and female larvae at 20 ºC and decremented to 2.43 and 2.47 days at 32.5 ºC, respectively. Similarly, the longest and the shortest male and female pupal duration was observed at 20 ºC (16.12 and 18.27 days) and 32.5 ºC (5.05 and 5.02 days), respectively. Adult male and female longevity was longest (42.83 and 58.44 days) at 20 ºC and shortest (16.05 and 14.02 days) at 32.5 ºC, respectively. Population parameters including R0, r, and λ ranged between 4.98-28.81 offspring, 0.0378-0.2001 d-1 and 1.0351-1.2065 d-1, respectively, when temperature increased from 20 to 27.5 ºC, proving about 5 folds enhancement in r. Generation time was 42.50 days at 20 ºC and decreased to 15.16 days at 32.5 ºC, respectively. Female wasp required at least 2.62 days at 27.5 ºC and maximum 8.18 days at 20 ºC to start oviposition. It is concluded that the population characteristics of H. hebetor were statistically superior at 27.5 ºC compared with those in other treatments and considering economy of rearing, 27.5 ºC along with 65±5 and 16:8 L:D h would be the optimum conditions for its propagation on G. mellonella larvae.

The orange pulvinaria scale, Pulvinaria aurantii Ckll. is the most important scale of citrus in the northern Iran. The lethal effects of chlorpyrifos, pyripropoxyfen, acetamiprid and palazin, alone and in combination with emulsifying oil, were evaluated on first-instar nymphs of P. aurantii. The experiment was conducted under natural condition in a randomized complete block design with 3 replications and 10 treatments, and treatments effect was compared 1, 7, 14 and 21 days after spraying. Moreover, the effect of these insecticides was investigated on duration of immature stages and female longevity of Cryptolaemus montrouzieri Mulsant. The activity of some detoxification enzymes (alpha-esterase, beta-esterase and glutathion-S-transferase) in third instar larvae was evaluated. The experiments on the ladybird were conducted under laboratory conditions at 26±1ºC, 75±5% RH and a photoperiod of 14:10 (L:D) h. The treatments with acetamiprid + oil, pyripropoxyfen + oil, chlorpyrifos + oil and palazin + oil had the highest mortality on first nymphal instar of the scale. The longest incubation period of C. montrouzieri was in chlorpyrifos treatment (8.13 days), and the shortest was in control (4.80 days). Moreover, among treatments the female longevity of C. montrouzieri was the longest in control (96.60 days), and shortest in chlorpyrifos treatment (53.50 days). Chlorpyriphos and acetamipirid caused the highest reduction in alpha-esterase and glutathion-S-transferase activities of the third larval instar of C. montrouzieri, respectively. Also, palizin had less negative effect on the activity of beta-esterase in comparison with other tested insecticides. The results of this study indicated that among tested compounds, palizin in combination with the oil is a suitable compound to control of the orange pulvinaria scale.

In this research, barley aphids in Mahidasht region of Kermanshah province were identified. Spatial distribution type and statistics for corn leaf aphid, Rhopalosiphum maidis (Fitch) were also studied and sequential sampling models were developed. Regular weekly sampling was carried out in 2015, 2016 and 2017. Each sampling date, 100 tillers were randomly visited and aphids were transferred to the laboratory for counting and identification. Taylor’s power law was used to determine spatial distribution type and statistics and sequential sampling models were developed according to Green (1970). Results revealed feeding of five species of aphids on barley including greenbug, Schizaphia graminum, rose-grain aphid, Metopolophium dirhodum, the English grain aphid, Sitobion avenae,corn leaf aphid, R. maidis and bird cherry-oat aphid, R. padi. Corn leaf aphid was more abundant during the season with 93.8%, 94.2% and 93.2% of aphids collected in 2015, 2016 and 2017, respectively. Low populations density of the other four species was observed every three years. Spatial distribution type of corn leaf aphid in barley field was determined as cumulative (b = 1.45). Sample size required in models with precision levels of 0.1 and 0.25 at mean aphid densities observed in the barley field (1.02 - 44.32 aphids per tiller) was 70 -524 and 11-84 tillers, respectively. In conclusion, sequential sampling model developed at the precision level of 0.1 was evaluated time consuming due to large sample size required, but the model at pest management precision level (0.25) was recommended for monitoring leaf corn aphid in barley fields.